The present invention relates to heart valve replacement and, in particular, to collapsible prosthetic heart valves. More particularly, the present invention relates to devices and methods for repositioning and anchoring collapsible prosthetic heart valves during the deployment procedure.
Prosthetic heart valves that are collapsible to a relatively small circumferential size can be delivered into a patient less invasively than valves that are not collapsible. For example, a collapsible valve may be delivered into a patient via a tube-like delivery apparatus such as a catheter, a trocar, a laparoscopic instrument, or the like. This collapsibility can avoid the need for a more invasive procedure such as full open-chest, open-heart surgery.
Collapsible prosthetic heart valves typically take the form of a valve structure mounted on a stent. There are two types of stents on which the valve structures are ordinarily mounted: a self-expanding stent and a balloon-expandable stent. To place such valves into a delivery apparatus and ultimately into a patient, the valve must first be collapsed or crimped to reduce its circumferential size.
When a collapsed prosthetic valve has reached the desired implant site in the patient (e.g., at or near the annulus of the patient's heart valve that is to be replaced by the prosthetic valve), the prosthetic valve can be deployed or released from the delivery apparatus and re-expanded to full operating size. For balloon-expandable valves, this generally involves releasing the entire valve, assuring its proper location, and then expanding a balloon positioned within the valve stent. For self-expanding valves, on the other hand, the stent automatically expands as the sheath covering the valve is withdrawn.
Despite the various improvements that have been made to the collapsible prosthetic heart valve delivery process, conventional delivery devices, systems, and methods suffer from some shortcomings. In conventional collapsible heart valves, the stent is usually anchored within the native valve annulus via the radial force of the expanding stent against the native valve annulus. If the radial force is too high, damage may occur to heart tissue. If, instead, the radial force is too low, the heart valve may prolapse or migrate, for example, into the left ventricle, requiring emergency surgery to remove the displaced valve. Because this radial anchoring partly depends on the presence of calcification or plaque in the native valve annulus, it may be difficult to properly anchor the valve in locations where plaque is lacking (e.g., the mitral valve annulus). Additionally, in certain locations, such as for mitral valve applications, the heart valve may require a lower profile so as not to interfere with surrounding tissue structures. Such a low profile makes it difficult for the valve to remain in place.
Moreover, it is not possible at this time, using available collapsible heart valves and delivery devices, to determine whether a valve assembly will function as intended without full deployment of the heart valve. However, due to anatomical variations between patients, a fully deployed heart valve may need to be removed from the patient if it appears that the valve is not functioning properly. Removing a fully deployed heart valve increases the length of the procedure and the risk of damage to surrounding tissue.
In view of the foregoing, there is a need for further improvements to the devices, systems, and methods for transcatheter delivery and anchoring of collapsible prosthetic heart valves, and in particular, self-expanding prosthetic heart valves. More particularly, a need exists for an arrangement that will enable the functioning of the valve to be ascertained prior to full deployment. Among other advantages, the present invention may address one or more of these needs.